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What would be a meaningful upgrade over an 8" SCT for EAA (for small DSOs)?

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#1 RazvanUnderStars

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Posted 15 May 2019 - 03:12 PM

i think the setup with an 8" SCT (with a reducer) is pretty common among EAA users (I use an Evo 8" + 0.63 reducer + ASI 294MC Pro myself). What would be an upgrade worth doing (i.e. worth saving for and more than "a tad better" ? I'm asking in the context of observing smaller objects (like galaxies) not nebulas.

 

  • a Hyperstar is one option, but because of the wider field, I think it's more appropriate for larger objects like nebulas.Same with a RASA 8".
  • a 9.25" SCT will of course bring more light (approx 1.33x  if only judging by the radius) but I'm not convinced it justifies selling the existing one and buying the new OTA + mount.
  • a 11" SCT will bring ~ 1.9x more light and more angular resolution. The downside is longer cooling. I'm not looking at an 11" RASA unless I win at a lottery :-)

 

Any other possibilities? 

 

Thanks.



#2 descott12

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Posted 15 May 2019 - 03:23 PM

I have never used the larger scopes but I understand that the weight difference is substantial. So a loss of portability and the purchase of a new mount is something to consider.  I also can't comment on the additional light gathering capacity, but regarding the Hyperstar:

 

The Hyperstar is awesome. Yes, the increased FOV is a big part of it but getting down to f2 is also really huge. Also, you don't have to worry about camera clearance behind/under the scope. I can't recommend the Hyperstar enough.



#3 clusterbuster

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Posted 15 May 2019 - 03:44 PM

i think the setup with an 8" SCT (with a reducer) is pretty common among EAA users (I use an Evo 8" + 0.63 reducer + ASI 294MC Pro myself). What would be an upgrade worth doing (i.e. worth saving for and more than "a tad better" ? I'm asking in the context of observing smaller objects (like galaxies) not nebulas.

 

  • a Hyperstar is one option, but because of the wider field, I think it's more appropriate for larger objects like nebulas.Same with a RASA 8".
  • a 9.25" SCT will of course bring more light (approx 1.33x  if only judging by the radius) but I'm not convinced it justifies selling the existing one and buying the new OTA + mount.
  • a 11" SCT will bring ~ 1.9x more light and more angular resolution. The downside is longer cooling. I'm not looking at an 11" RASA unless I win at a lottery :-)

 

Any other possibilities? 

 

Thanks.

A C9.25 or a C11 are both FINE TELESCOPES, I have had a lot of Telescopes, I think that Celestron and Meade produce Very GOOD Telescopes !

Mark



#4 StarryHill

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Posted 15 May 2019 - 04:17 PM

In my experience with a RASA11, switching to Hyperstar/RASA would be a step in the wrong direction if you are primarily interested in galaxies beyond the few big ones. Galaxies, like planets, do better with greater focal length, not lesser focal length that comes with Hyperstar/RASA. 

 

So the 9.25 and 11 SCTs would be steps in a better direction and would provide a bit more resolution than your 8". Would they be worth the cost? Only you can decide that.

 

How are results now with your 8" at f/6.3 and at f/10 on small galaxies? If you are happy with them, why change?


Edited by StarryHill, 15 May 2019 - 08:54 PM.

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#5 descott12

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Posted 15 May 2019 - 05:05 PM

Another thing to consider that I forgot to mention above is possibly switching cameras. I recently went thru the same situation of trying to see small spirals better. The 294 MC is great camera but it has large, color pixels.  That works well for large, diffuse, colorful objects but not so much with for small monochrome objects. When I started using my 178 MM, I went from an image scale of about 2.5 to about 1.1 and I was able to see fine details way better (like the jet in M87 - impossible to see with the 294, but easy with the 178).



#6 Starman81

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Posted 15 May 2019 - 05:22 PM

I only know EAA theoretically but I know GAS (Gear Acquisition Syndrome) very well when I see it and you have seem to caught it... I can't blame you, I fantasize about bigger and 'better' setups all the time as well.

Your setup is perfect for what you want to do and those other options unnecessarily add weight, cost and for limited upside and would require a beefier mount or at least a beefier tripod.

#7 Ptarmigan

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Posted 15 May 2019 - 06:54 PM

I used the C9.25 and very pleased with it. cool.gif waytogo.gif



#8 RazvanUnderStars

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Posted 15 May 2019 - 09:34 PM

I'll confess to GFS (Gear Fantasy Syndrome) :) Indeed, the current setup is in a sweet spot, I was merely curious about the upgrade paths (and this answers StarryHill's question as well).

 

 

I only know EAA theoretically but I know GAS (Gear Acquisition Syndrome) very well when I see it and you have seem to caught it... I can't blame you, I fantasize about bigger and 'better' setups all the time as well.

Your setup is perfect for what you want to do and those other options unnecessarily add weight, cost and for limited upside and would require a beefier mount or at least a beefier tripod.


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#9 RazvanUnderStars

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Posted 15 May 2019 - 09:40 PM

That's a very good point (and certainly a cheaper alternative). I'll check https://agenaastro.c...yers-guide.html for a monochrome camera more suitable for galaxies. Thanks.

 

Another thing to consider that I forgot to mention above is possibly switching cameras. I recently went thru the same situation of trying to see small spirals better. The 294 MC is great camera but it has large, color pixels.  That works well for large, diffuse, colorful objects but not so much with for small monochrome objects. When I started using my 178 MM, I went from an image scale of about 2.5 to about 1.1 and I was able to see fine details way better (like the jet in M87 - impossible to see with the 294, but easy with the 178).



#10 tgrlx200

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Posted 15 May 2019 - 10:33 PM

I think the scope is fine, also. The camera's are what have revolutionized what we are able to see. In my 10"lx200, in the eyepiece M27 was a gray smudge. With my ZWO 224, it is a bow tie filled with color. And thst is from a severely light polluted site. I agree with descott 12, the camera is what will dramatically change your setup for the better. And they get easier and easier to operate with better results as time goes on. In 5 or 10 years, we will be amazed at what features the new camera's will offer.

Edited by tgrlx200, 15 May 2019 - 10:36 PM.


#11 bobhen

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Posted 16 May 2019 - 07:51 AM

Stop using the 6.3 reducer and you’ll get larger image scale. If your current mount can’t handle imaging at the longer FL, then you need a better mount with really excellent tracking and a larger load capacity.

 

Bob


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#12 Stargazer3236

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Posted 16 May 2019 - 08:27 AM

I would suggest the ZWO ASI290mm. It has excellent pixel size and is very sensitive. It has become one of the best monochrome cameras available. In a C8, it does really short work on galaxies. Typically, many CNers use the 290mm, like myself, at F/5. Since it is a sensitive sensor, 2.3 mp, it will frame single or close doubles and triple galaxy clusters easily. Astrojedi has displayed many galaxies images using his 290mmm @F/5. The detail is incredible. Still, I would recommend the Asi224mc or Asi385of if you want color, with a small chip sensor.


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#13 Rickster

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Posted 16 May 2019 - 02:07 PM

Here is another vote for the 290MM.  It really does the trick on distant galaxies. 

 

And if you want more FOV than the 290 offers, the 183 mono would be the same, only bigger.  (Despite the 290 mono's superb performance, I have given up on using it in my 16 inch scope.  The small FOV is too much of a pain at my focal lengths.  But Astrojedi has had excellent results in an 8 inch SCT).

 

Or, the 1600 mono is highly regarded on the AP forums.


Edited by Rickster, 16 May 2019 - 02:10 PM.


#14 RazvanUnderStars

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Posted 16 May 2019 - 03:14 PM

Thanks Stargazer3236 and Ricksters for the reminders about the mono cameras. Indeed, for galaxies I'd rather have resolution than colour for EAA.

 

Bobhen, with a mono camera I'll also try taking out the reducer (the downside is going back to f/10 but hey, it's free so worth comparing).

 

I might give a second try to using my 10" Orion dob which I didn't mention originally since I had used it mostly for visual. It's f/4.7, just that it's more sensitive to wind-induced vibration so really need a windless night or a sheltered location; but even buying a wind shelter and a motorized focuser will be much cheaper than upgrading the scope. 



#15 Astrojedi

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Posted Today, 09:56 AM

It is unlikely that even with a 10” you will be able to achieve better resolution than a C8. An 8” scope provides a resolution that significantly exceeds what seeing permits. I also chased larger aperture for resolution and for seeing small distant stuff but ultimately realized the folly in that.

To realize even what a C8 is capable of you will need to get a more sensitive smaller pixel monochrome camera, precisely collimate and completely eliminate tracking errors. Since I use commercial mounts, the low read noise and very high QE sensors such as the 290 allow me to use short exposures and FWHM based filtering in SharpCap to eliminate tracking errors and bad subs and maximize resolution.

While it can be done, all of this will be much harder with a larger and heavier 10” scope with no immediate benefit that I can see. I would only move to a larger scope when you have exhausted the capabilities of the 8” otherwise you are just trying to use aperture to compensate for other issues in your EAA/imaging process.

 

I would recommend you start with the 290 mono and a F5 reducer and learn to use SharpCap for high resolution imaging. Once you have mastered that then you can decide whether you need a larger scope. Hope this helps.


Edited by Astrojedi, Today, 10:17 AM.

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#16 Ptarmigan

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Posted Today, 02:22 PM

I would suggest the ZWO ASI290mm. It has excellent pixel size and is very sensitive. It has become one of the best monochrome cameras available. In a C8, it does really short work on galaxies. Typically, many CNers use the 290mm, like myself, at F/5. Since it is a sensitive sensor, 2.3 mp, it will frame single or close doubles and triple galaxy clusters easily. Astrojedi has displayed many galaxies images using his 290mmm @F/5. The detail is incredible. Still, I would recommend the Asi224mc or Asi385of if you want color, with a small chip sensor.

I use the IMX385 in the Altair GPCAM3 and like it a lot. cool.gif waytogo.gif




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